Radio frequency IC tags are currently widely used in information management and logistics control of articles. The radio frequency IC tags are also affixed to metallic materials used as base members for structures. Such IC tags are used for assembly control, inventory control, and the like of structures. The radio frequency IC tag, such as those described above, includes a small IC chip and a small antenna. The small IC chip is adapted to record information thereon. The small antenna is operative to transmit information stored on the IC chip wirelessly. The radio frequency IC tag may, for example, be applied as below. Specifically, a small IC chip measuring about 0.4 mm wide, about 0.4 mm long, and about 0.1 mm high is affixed to a metallic material at a location near a center of a half-wave (λ/2) dipole antenna.
FIGS. 7A and 7B are views showing a state in which a conventional radio frequency IC tag is affixed to a metal pipe. FIG. 7A is a perspective view and FIG. 7B is a fragmentary cross-sectional view taken along line E-E of FIG. 7A. As shown in FIGS. 7A and 7B, a radio frequency IC tag 41 is affixed to a surface of a metal pipe 42 using an adhesive or the like. With this arrangement, information stored on the IC chip (that is, control information concerning attributes of the metallic material, such as material, dimensions, and the like) can be read in a non-contact fashion by bringing a reader (not shown) close to the radio frequency IC tag 41.
Another technique for controlling information is also widely known. In this technique, an IC tag is affixed to a metallic object, such as an aluminum packaging material, a metal can, and the like. The IC tag contains information of various kinds that range from contents, manufacture, an expiration date, and the like. In applications such as that cited above, in which the IC tag is affixed to a metallic object, a measure is taken to prevent reading of the IC tag from becoming erratic as affected by a magnetic field produced by the metallic object. The measure taken may, for example, be a laminated structure of a resin plate, an insulation film, and an IC tag stacking of one on top of another. The resin plate includes a ferrite powder with a predetermined magnetic permeability (see, for example, Japanese Patent Laid-open No. 2004-127057 (paragraph numbers 0014 through 0029, and FIG. 1), hereinafter referred to as “Patent Document 1”).
Conventionally, the radio frequency IC tag 41 is affixed to the surface of the metal pipe 42 as shown in FIGS. 7A and 7B. This arrangement causes the radio frequency IC tag 41 to protrude from the surface of the metal pipe 42. There is therefore a problem in that the radio frequency IC tag 41 tends to peel off the surface of the metal pipe 42. Take, for example, a case, in which a radio frequency IC tag using a strip antenna is to be affixed to a metallic material. In such a case, the radio frequency IC tag is affixed to the metallic material by way of a relatively thick insulation film interposed therebetween. This is done to prevent radio frequency characteristics of the antenna from being affected by the metallic material. This results in the radio frequency IC tag 41 protruding so excessively from the surface of the metal pipe 42 that the IC tag 41 is easily peeled off.
In the technique disclosed in Patent Document 1, the resin plate, the insulation film, and the IC tag are stacked one on top of another and affixed to the metallic object to prevent radio waves transmitted from the IC tag from being affected by the metallic object. This arrangement results in the IC tag protruding substantially from the surface of the metallic object. The IC tag therefore may easily come off.